Hi Rudi,
The neck/head was a little sphere above the lower sphere. I stretched some of the lower points down to make a long protrusion and then moved that into the lower body and booleaned them together, then ran a filet on the edge.

once you start pulling points on 2 spheres, it should be apparent for you how to get the shape you want. Remember when you go to do your booleans to stick things "completely through" each other, then you can make that intersection smooth with a filet (Same as with the legs attaching to the body..)

What kind of rubber duck were you looking for? the 3 stooges classic gag one?